Electrochemical Nucleation Research Articles

Theory of electrochemical nucleation and growth—revisited?

Theory of electrochemical nucleation and growth—revisited?

New Insight into Electrochemical Nucleation and Growth of Metal Nanoparticles through Multiscale Approach

Nowadays, supporting metal nanoparticles have attracted much interest due to their fascinating physio-chemical properties and potential application in fuel cells, sensors, catalysis, solar to fuel devices and among others. One of the interesting issues from engaging physiochemical properties of supporting nanoparticles is to understand their nucleation and growth mechanism in order to get a good control of their structural and morphological parameters. Although studied for decades, however, the full details are still out of reach [1]. In this presentation, we will first review the classical theory of nucleation and growth and secondly present our recent finding and theoretical development on the growth of an isolated metal nanoparticle using a combined experimental (linear sweep voltammetry, chronoamperommetry and FESEM) and multiscale modelling approach [2-5]. In this presentation we focused on the modelling approach. The use of such a multiscale framework allows studying nanoscale electrochemical deposition as a whole, without the need to assume a dominant growth mechanism such as diffusion or kinetic control [2-5]. The simulation results reveal that the existing theory of nucleation and growth is only valid for some specific conditions. Some of the findings will be discussed in this presentation.

Pulse Plating of Zinc for Highly Efficient Rechargeable Metal Redox Flow Batteries

In current research, electrochemical energy storage systems have gaining interest because they constitute an essential element in the development of sustainable energy technologies. Among them, rechargeable flow batteries (RFBs) are one of the most promising technology for the integration in grid-connected electricity, especially if combined with unpredictable and intermittent renewable energy sources, due to their high efficiency, power/energy independent sizing and room temperature operation. At the moment, among all RFBs systems, the most investigated and advanced technology is the vanadium based RFB, characterized by an energy efficiency equal to 80% and energy density ranging 15-45 Wh/l. However, nowadays the main bulk of research is focused on finding an economically convenient and technically competitive flow battery chemistry, able to ensure long lifetime and high energy efficiency. A zinc-iron RFB with low cost and high energy density will be presented. In particular, inorganic electrolytes based on high soluble salts have been developed, achieving a charge density of 30-70 Wh/l. The electrochemical nucleation and growth of zinc onto a carbon felt current collector in continuous and pulse charging of the battery is studied, showing the achievable improvements in terms of efficiencies and stability of the RFB over charging time. The combination of high energy efficiency of the Zn-Fe RFB with its ability to withstand a large number of charge/discharge cycles and the low cost, makes this battery system suitable for energy storage applications.

Electrochemical Nucleation of Silicon in Ionic Liquid-Based Electrolytes

Silicon is widely applied in a high number of industrial technologies, including different types of electronics, solar energy conversion and electrochemical energy storage. This extensively studied material has an exceptionally high theoretical capacity, more than ten times higher compared to the currently used graphite anodes in Li-ion batteries [1]. However, its main disadvantage is the huge volume expansion upon alloying with lithium, inducing disintegration of the electrode material, loss of electrical contact, poor reversibility and a rapid capacity fade [1]. It has been established that Si applied in a nanostructured or nanoparticulate form displays an enhanced electrochemical stability. Therefore, advanced production technologies have to be implemented in order to obtain cost-effectively the required electrochemically stable Si morphologies.Electrochemical methods offer a simple and low-cost deposition process. Furthermore, the electrodeposition is a versatile technique, allowing control of the morphology by adjusting the experimental conditions and obtaining deposits on different substrate geometries. However, due to the very low reduction potential and high reactivity of silicon precursors, it is impossible to deposit this element in aqueous electrolytes. Therefore, a broad variety of alternative media, including high temperature molten salts (HTMS) [2], conventional organic solvents [3] and ionic liquids (ILs) [4] has been researched.It is established that the initial stages of electrodeposition play an important role for the physical properties, stability and functional behavior of the final deposit. For example, homogeneous distribution of a high number density of small Si crystals would be beneficial for the electrochemical stability of the deposit during lithiation. Therefore, the nucleation and growth process of silicon deserves a special attention. Initial studies on the formation of Si nuclei in HTMS have been recently reported [2]. It was found that the diffusion limited nucleation process in HTMS (i.e. KF-LiF-K2SiF6) is instantaneous, followed by 3D growth [2]. However, due to the high temperatures (T > 800oC) and difficulties to perform the Si deposition economically in these electrolytes the research interest has turned to low temperature molten salts (LTMS).In our study we analyze the initial stages of Si electrodeposition in IL electrolytes by interpreting the chronoamperometric data (fig.1a) with a model accounting nucleation and growth under diffusion limitation, established by Scharifker et al. [5-7], eq.1. Vitreous carbon was selected as an inert substrate for the experiments and 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide [BMP][TFSI] containing SiCl4 was chosen as an electrolyte.The current transients were quantitatively interpreted by a non-linear fitting procedure, applying a model equation for three-dimensional nucleation, eq.1. Eq.1 was modified with a term describing the surface charging phenomena, observed at the beginning of the silicon reduction, approximated to an exponential decay after Langmuir adsorption kinetics, eq.2. To prove the validity of this procedure, we extracted the charging currents (fig.1b) and fitted the resulting curves with the non-modified equation for 3D nucleation, where the respective output parameters remained nearly identical. According to eq.(3), the data for P1 should be constant for all fitted curves (i.e. potentials) since this parameter does not depend on other variables. This allows the value of the diffusion coefficient D =1.3×10−8 cm2 s−1 to be calculated. D was additionally confirmed by the analysis of the current maxima [5,6]. The data for the nucleation frequency, A and the number density of active sites, N0 obtained from the best fit are presented in Fig. 1c and show the typically observed linear increase as a function of the overpotential,η [7].Furthermore, we characterized the nucleation process by analyzing the current maxima in dimensionless coordinates (fig. 1d). According to the analysis the initial stages of the Si phase formation display an instantaneous behavior, showing a progressive character with decreasing the applied overpotential. The theoretically evaluated values for N0 correlate well with the crystal number density N, acquired by scanning electron microscopy. The talk will cover the main aspects of the electrochemical nucleation of Si in non-aqueous electrolytes and will provide a discussion on the major challenges towards understanding this process.

Nitrogen Bubbles at Pt Nanoelectrodes in a Nonaqueous Medium: Oscillating Behavior and Geometry of Critical Nuclei.

Gas bubble evolution is present in many electrochemical and photoelectrochemical processes. We previously reported the formation of individual H2, N2, and O2 nanobubbles generated from electrocatalytic reduction of H+ and oxidation of N2H4 and H2O2, respectively, at Pt nanodisk electrodes in an aqueous solution. All the nanobubbles formed display a dynamic stationary state of a three-phase boundary with an invariant residual current. Here, we test the hypothesis that gas nanobubbles can also be electrogenerated in a nonaqueous medium. Interestingly, we found oscillating bubble behavior corresponding to nucleation, growth, and dissolution in dimethyl sulfoxide and methanol. One possible explanation of the oscillation mechanism is provided by the instable dynamic equilibrium between the gas influx due to supersaturation and outflux due to Laplace pressure. Furthermore, the critical gas concentrations for N2 nanobubble nucleation are estimated to be 148, 386, 200, and 16 times supersaturation and the contact angles of the critical nuclei to be 164°, 151°, 160°, and 174° in water, dimethyl sulfoxide, ethylene glycol, and methanol, respectively. This is the first report on electrochemical nucleation of gas bubbles in nonaqueous solvents. Our electrochemical gas bubble study based on a nanoelectrode platform has proven to be a prototypical example of single-entity electrochemistry.

Optical monitoring of the electrochemical nucleation and growth of silver nanoparticles on electrode: From single to ensemble nanoparticles inspection

The electrochemical nucleation and growth of nanoparticles (NPs) on an electrode surface at a constant potential is traditionally followed by recording the resulting current density during the experiment. The obtained chronoamperometric transients are average measurements, making it difficult to separate individual NP behaviors and to study their cross-talks. Herein, the recently developed Backside Absorbing Layer Microscopy (BALM) is employed to monitor optically in situ and operando the electrodeposition of silver NPs. This latter technique exploits a pseudo-antireflective and metallic contrast layer and allows both sub-nanometer vertical and sub-micrometer spatial resolutions. The information from the recorded movies is readily exploited to study the NP electrodeposition at the single entity level. The image sequences allow quantifying the local electrodeposition of nanomaterials onto the electrode surface, probing the NP dynamics through the extraction of single optical NP growth transients, and analyzing the effect of the neighboring nuclei on the growth of individual NPs.

Electrochemical nucleation and growth of Pt nanoflower particles on reduced graphite oxide with electrooxidation of glucose.

Electrochemical deposition of platinum nanoflower particles (PtNFPs) on reduced graphite oxide, rGO/GCE, using H2PtCl6 electrolyte in H2SO4 solution was investigated by chronoamperometry (CA). The experimental i-t curves measured at different overpotentials were analyzed and compared with theoretical curves obtained for the two limiting cases of the 3D nucleation and growth model, as described by Scharifker and Hills. The effect of deposition overpotential on the deposition process was evaluated. Through comparing potentiostatic current-time transients with the Scharifker-Hills model, a transition from instantaneous to a mixed kind of progressive-instantaneous nucleation was observed when increasing the deposition overpotential. CA results clearly show that the electrodeposition processes are diffusion-controlled (D0 = 2.77 × 10-5 cm2 s-1). A finer distribution of PtNFPs with an average size of ∼70 nm was obtained in 1.0 mM H2PtCl6 electrolyte in a 0.5 M H2SO4 solution. The as-prepared PtNFP/rGO catalyst shows 1.5 times higher activity than rGO/GCE, and the catalytic activity towards glucose oxidation is about many fold higher than that of the rGO/GCE and bare platinum electrode.

Theoretical modeling of electrochemical nucleation and growth of a single metal nanocluster on a nanoelectrode.

Theory of the initial stages of electrochemical formation and growth of a single metal nanocluster on an indifferent nanoelectrode has been developed and analyzed. General theoretical time dependences of the current and nanocluster size have been presented for the case of diffusion controlled growth at potentio- and galvanostatic deposition, and cyclic voltammetry.

Current atomic-level understanding of electrochemical nucleation and growth on low-energy surfaces

This review presents recent progress in the understanding of electrochemical phase formation on low-energy substrates, which is essential for metal electrodeposition and the design of stable batteries. Advanced characterization techniques and ultrasensitive electrochemical instrumentation give access to experimental data that were not available a few years back. Besides, the continuous development of theoretical models gradually provides a more complete description of multiple nucleation. However, important contradictions between experimental findings and theoretical formulations are found: nonclassical growth pathways, single-atom critical clusters, and cluster densities that are orders of magnitude higher than the calculated number of active sites. New descriptions of the initial steps of nucleation are discussed. They are grounded on nucleation being a nonactivated process, in which the initial stages of phase formation could involve simply adsorbed atoms collapsing into larger clusters driven by minimization of the overall interfacial energy. Finally, some remaining challenges and possible research directions are outlined.

Electrodeposition and Characterization of Nanostructured Palladium-Copper Alloy on Graphite Substrate

The electrodeposition of Pd-Cu alloy films on graphite electrode from industrial aqueous solution was investigated using electrochemical techniques. Cyclic voltammetry and linear sweep voltammetry techniques were performed to understand the deposition process. The deposition was conducted using both chronoamperometric and chronopotentiometric techniques. All the affecting parameters such as bath agitation, bath temperature and deposition time, were studied to get the optimum preparation conditions of palladium copper alloy film. The mechanism for electrochemical nucleation reaction and growth of Pd Cu alloy films was studied by applying the Scharifker and Hills model. The nucleation mechanism consisted of a mix between progressive and instantaneous growth mechanisms. The structural characterization by X-ray diffraction indicates the formation of Pd-Cu binary alloy cubic phase. The crystallite size of deposited films were 23 and 14 nm with and without TEA, respectively. The surface morphology of the Pd-Cu revealed that a smooth homogenous film was formed with cauliflower dendritic structure.

Understanding the initial stages of Si electrodeposition under diffusion kinetic limitation in ionic liquid-based electrolytes

The electrochemical nucleation and growth of silicon on a vitreous carbon substrate in 1-butyl-1-methylpyrrolidinium bis (trifluoromethylsulfonyl) imide [BMP][TFSI] is investigated by interpreting potentiostatic current transients. Theoretical model for three-dimensional nucleation, accounting for propagation and overlap of diffusion zones is applied for quantitative characterization of the process. In addition to the established methodology of current maxima analysis in dimensionless coordinates our approach involves interpretation of the entire current transient by a non-linear fitting procedure. The initial stages of the Si phase formation display an instantaneous behavior, showing a tendency for more progressive character with decreasing the applied overpotential. The results attained by analysis of the current transients are confirmed by scanning electron microscopy (SEM). The chemical composition of the deposit is determined by X-Ray Photoelectron Spectroscopy (XPS).

High-Throughput Correlative Electrochemistry-Microscopy at a Transmission Electron Microscopy Grid Electrode.

As part of the revolution in electrochemical nanoscience, there is growing interest in using electrochemistry to create nanostructured materials and to assess properties at the nanoscale. Herein, we present a platform that combines scanning electrochemical cell microscopy with ex situ scanning transmission electron microscopy to allow the ready creation of an array of nanostructures coupled with atomic-scale analysis. As an illustrative example, we explore the electrodeposition of Pt at carbon-coated transmission electron microscopy (TEM) grid supports, where in a single high-throughput experiment it is shown that Pt nanoparticle (PtNP) density increases and size polydispersity decreases with increasing overpotential (i.e., driving force). Furthermore, the coexistence of a range of nanostructures, from single atoms to aggregates of crystalline PtNPs, during the early stages of electrochemical nucleation and growth supports a nonclassical aggregative growth mechanism. Beyond this exemplary system, the presented correlative electrochemistry-microscopy approach is generally applicable to solve ubiquitous structure-function problems in electrochemical science and beyond, positioning it as a powerful platform for the rational design of functional nanomaterials.

Influence of the Formation Current Density on the Transport Properties of Galvanostatically Formed Model‐Type Solid Electrolyte Interphases

AbstractDuring the production of commercial lithium‐ion batteries, the solid electrolyte interphase (SEI) on the graphite particles of the negative electrode is typically formed through galvanostatic protocols with low current densities. Consequently, SEI formation is a time‐consuming and rather expensive production step. In order to better understand the influence of the formation current density on the transport of ions and molecules across the SEI, we formed model‐type SEIs on planar glassy carbon electrodes under galvanostatic control. In accordance with the expectations from electrochemical nucleation and growth theory, we find that the transport of both ions and molecule becomes slower with increasing formation current density. However, it is remarkable that the ion transport is slowed down more strongly than the molecule transport. We show that at high formation current densities of about −71 μA cm−2, our model‐type SEIs clearly exceed the area‐specific resistance tolerable in commercial lithium‐ion cells.

In Operando Optical Visualization of Br5 - electrochemistry with a Planar Glass Battery for Zn/Br Flow Batteries

Zn/Br flow batteries are one of the promising technologies for stationary energy storage. Bromine complexing agents have been used to form phase-separated liquid polybromide charging products. However, dynamic and microscopic understandings of the nucleation and growth of the polybromides are limiteddue to the beam-sensitivity and complexity of these compounds and their surrounding electrolytes. In this communication, we report an in operando platform composed of dark field light microscopy and a transparent planar electrochemical cell to dynamically reveal the electrochemical nucleation and formation of polybromides. Using our platform, we confirm the liquid nature, reveal the pinning effect (strong interaction with Pt), memory effect (surface residual), self-discharge of the polybromide product, and discover over-oxidation as a side reaction for ZBB. We also conclude that the electrochemically formed droplets are mainly MEPBr5,rather than previously reported MEPBr3 with in situ Raman spectroscopy. These results provide mechanistic insightsinto the role of ionic liquid complexing agents and Zn/Br battery design. The in operando visualization platform can also be applied to study other unstable or transient products or intermediates in electrochemical reactions in ambient environment.

Electrodeposition of cobalt nanoparticles: An analysis of the mechanisms behind the deviation from three-dimensional diffusion-control

Electrochemical nucleation and growth of cobalt nanoparticles on aluminium was investigated by potentiostatic electrodeposition from cobalt sulphate solutions buffered with boric acid. At sufficiently low overpotential, the experimental current transients could be fairly reproduced by a mathematical model describing nucleation and growth under mixed kinetic-diffusion control, yielding an estimated number of particles per surface area in agreement with the SEM analysis of the deposits. However, the model gave estimates for the charge-transfer kinetic constant several orders of magnitude lower as compared to the Tafel analysis of cobalt electrodeposition on a previously electrodeposited cobalt film. This deviation can be explained by the inhibition of the direct attachment of metal ions, which can be induced by the adsorption of hydrogen onto cobalt particles and/or the formation of stable nanocluster aggregates. The implemented model failed to reproduce the current transients generated at larger overpotential values. A revision of the implemented mathematical model overcoming this limitation is proposed.

Control of the adhesion strength between nickel replica and copper mold by electrochemical nucleation of lead

The failure to release nickel replica from its copper mold occurs sometimes, in particular, when nickel replica is thin, large and has microstructures such as micro prism arrays. The failure is induced by improper adhesion strength between nickel replica and its copper mold. When the adhesion strength becomes too strong, the release of nickel replica from its copper mold can lead to poor surface finish or severe damages on nickel replica and/or copper mold; when the adhesion strength becomes too weak, premature release of nickel replica can happen due to internal stress that has been built up during electrochemical deposition, leading to the failure of electroforming process. To address this challenge, this paper proposes a simple and effective electrochemical approach to control the adhesion strength. The approach is to electrochemically deposit a certain density of lead nuclei on copper mold before electrochemically depositing nickel. Our experiments indicate that: (1) lead nuclei density can be conveniently controlled by nucleation duration time and electrical current; (2) lead nuclei density affects significantly the adhesion strength and hence can be used to control the adhesion strength; (3) the release of nickel replica from its copper mold becomes easy and the associated surface roughness is improved significantly when an optimal lead nuclei density is electrochemically deposited on its copper mold.

Electrochemical nucleation and growth of Zn-Ni alloys from chloride citrate-based electrolyte

In this work, the effects of deposition potential, [Ni2+]/[Zn2+] molar ratio, pH and bath temperature on the electrocrystallization mechanism of ZnNi alloy from an aqueous solution containing zinc chloride (ZnCl2), nickel chloride (NiCl2) and tri‑sodium citrate as complexing agent were studied. The Zn–Ni alloys were deposited from solutions with different molar ratios (0.25; 1; 2; 4), pHs (1.5; 3; 4) and bath temperatures (20; 40; 60°C). Scharifker and Hills model, used to analyze the potentiostatic current transients, revealed that in a plating bath containing low [Ni2+]/[Zn2+] molar ratios (R≤1), the nucleation mechanism was instantaneous with a typical three-dimensional (3D) growth process, regardless of the bath pH and temperature. In Ni-rich electrolytes (R≥2), the nucleation becomes more consistent with the theoretical progressive nucleation type. The nuclei number density increased with increasing the applied cathodic potential and bath pH and decreases for both of high [Ni2+]/[Zn2+] molar ratios in solution and elevated plating temperatures. The morphological, compositional and structural characterizations of the deposits were carried out using Field-Emission Scanning Electron Microscopy (FESEM), Wavelength Dispersive X-ray Fluorescence Analysis (WDXRF) and X-ray diffraction (XRD) respectively. The obtained results revealed that nickel content of the coatings was increased by increasing cathodic potential and [Ni2+]/[Zn2+] molar ratio and ranged between 5.82 and 29.3wt% (6.44–31.59at.%). ZnNi alloys coated at room temperature from an equimolar ([Ni2+]/[Zn2+]=1) bath were composed of a mixture of two major phases: the δ-phase (Ni3Zn22) with a monoclinic structure and the γ-phase (NiZn3) with an orthorhombic structure, while for deposits obtained in Ni-rich bath, the γ-NiZn3 phase was particularly prevailing. A mechanism of anomalous co-deposition of zinc with nickel is proposed and discussed.

Nucleation and growth kinetics of electrochemically deposited ceria nanostructures for high-temperature electrocatalysis

Cathodic electrochemical deposition, a simple and cost-effective route for fabricating ceria nanostructures, has attracted much attention in catalysis and renewable energy technologies. However, electrochemical nucleation and growth mechanisms that determine the nanoscale architecture of ceria films during deposition have not yet been clarified. In this study, we analyze current and mass-time transients and thin film microstructures as functions of applied potential and temperature. We then examine these results in light of analytical models for the determination of relative nucleation rate, nuclei density, and diffusivity of Ce ion during ceria electrocrystallization. As applied potential and temperature decrease, the reduced deposition rate allows nuclei to branch, leading to more ‘petal’-like nanostructures with high specific surface areas. These optimized ceria nanostructures greatly improve the hydrogen electro-oxidation rate and reduced electrode resistance when coated onto a model electrode that simulates a Ni/yttria-stabilized zirconia composite anode utilized in solid oxide fuel cells.

Electrochemical nucleation and optical characterization of highly oriented Bi clusters on Cu substrate

The electrochemical nucleation and growth of bismuth (Bi) crystallites on copper substrates were investigated using cyclic voltammetry and chronoamperometry measurements, and scanning electron microscopy (SEM). The experimental current transients were analyzed according to the Scharifker and Hills and Mirkin-Nilov and Heerman-Tarallo models. At relatively low overpotentials and low Bi concentration, Bi deposition can be described by a model involving progressive nucleation on active sites and 3D diffusion-controlled growth. At higher Bi concentration, the growth mechanism shifts to the instantaneous nucleation mode. These results were also confirmed by SEM analysis. The values of some kinetic parameters such as the nucleation rate, the number density of active sites and the diffusion coefficient of Bi3+ ions were also calculated using different theoretical approaches. X-ray diffraction measurements revealed that the Bi crystallites grow in the rhombohedral crystal structure along the [012] direction. The optical properties of the dispersed Bi nanoparticles on the Cu surface were discussed in the ultraviolet-visible (UV–Vis) wavelength range. It was found that the UV–Vis spectrum exhibit a strong resonant optical absorption on the surface with the smallest Bi crystallite size (200 nm).

(Invited) In-Situ Investigation of the Role of Boric Acid during the Electrodeposition of Cobalt

As interconnect dimensions continue to decrease, copper damascene faces significant challenges1. As a result, alternative metals such as cobalt are actively being explored. Because the standard reduction potential for cobalt is more cathodic than that of hydrogen evolution, the solution pH is a critical consideration for the plating process. Boric acid is a common component in plating solutions used for cobalt electrodeposition. It is believed that boric acid acts as a buffering agent that helps to stabilize bath pH and to prevent formation of cobalt hydroxide precipitate on the substrate2-4. Typically, maximum buffering occurs when the pH equals the pKa for the weak acid. Thus, it is not well understood how an additive such as boric acid, with a pKa value of 9.275, can act as a buffer in typical cobalt electroplating baths6-9 which often have pH ranges of 2-5. The aim of this work is to provide an improved understanding of the role of boric acid on the electrodeposition of cobalt. It is important to first determine the effects of boric acid on surface pH during cobalt deposition. We present a technique for in-situ monitoring of surface pH as a function of applied plating current density. This is done using a tungsten microelectrode which can function as an indicator electrode for the hydrogen ion activity10-12. Results for plating cobalt from a virgin makeup solution (VMS) will be compared to those containing boric acid to demonstrate that this additive acts as a buffer at the electrode surface where pH values drastically increase during metal deposition. Electrochemical impedance spectroscopy (EIS) data will aid in understanding the surface adsorption behavior as well as the coulombic plating efficiency. In addition to surface specific information, potentiometric titration data will be presented to explain buffering effects in the bulk electrolyte. References R. Akolkar, "Current Status and Advances in Damascene Electrodeposition," Encyclopedia of Interfacial Chemistry, pp. 24-31, 2018.N. Zech and D. Landolt, "The influence of boric acid and sulfate ions on the hydrogen formation in Ni-Fe plating electrolytes," Electrochimica Acta, vol. 45, no. 21, pp. 3461-3471, 2000.J. P. Hoare, "On the Role of Boric Acid in the Watts Bath," Journal of The Electrochemical Society, vol. 133, no. 12, pp. 2491-2494, 1986.J. Santos, R. Matos, F. Trivinho-Strixino and E. C. Pereira, "Effect of temperature on Co electrodeposition in the presence of boric acid," Electrochimica Acta, vol. 53, pp. 644-649, 2007.D. R. Lide, CRC Handbook of Chemistry and Physics, Boca Raton, FL: CRC Press, 2005, p. 1274.M. A. Rigsby, L. J. Brogan, N. V. Doubina, Y. Liu, E. C. Opocensky, T. A. Spurlin, J. Zhou and J. D. Reid, "The Critical Role of pH Gradient Formation in Driving Superconformal Cobalt Deposition," Journal of The Electrochemical Society, vol. 166, no. 1, pp. D3167-D3174, 2019.Y. Hu and Q. Huang, "Effects of Dimethylglyoxime and Cyclohexane Dioxime on the Electrochemical Nucleation and Growth of Cobalt," Journal of The Electrochemical Society, vol. 166, no. 1, pp. D3175-D3181, 2019.C. H. Lee, J. E. Bonevich, J. E. Davies and T. P. Moffat, "Superconformal Electrodeposition of Co and Co–Fe Alloys Using 2-Mercapto-5-benzimidazolesulfonic Acid," Journal of The Electrochemical Society, vol. 156, no. 8, pp. D301-D309, 2009.D. Josell, M. Silva and T. Moffat, "Superconformal Bottom-Up Cobalt Deposition in High Aspect Ratio Through Silicon Vias," ECS Transactions, vol. 75, no. 2, pp. 25-30, 2016.S. E. S. E. Wakkad, H. A. Rizk and I. G. Ebaid, "The Electrochemical Behavior of the Tungsten Electrode and the Nature of the Different Oxides of the Metal," The Journal of Physical Chemistry, vol. 59, no. 10, pp. 1004-1008, 1955.J. O. Park, C.-H. Paik and H. C. Alkire, "Scanning Microsensors for Measurement of Local pH Distributions at the Microscale," Journal of The Electrochemical Society, vol. 8, no. 143, p. 174, 1996.E. Webb and R. Alkire, "Pit Initiation at Single Sulfide Inclusions in Stainless Steel," Journal of The Electrochemical Society, vol. 146, no. 6, p. B280, 2002.